A photolithography technology comprises the steps of forming a resist film made of a resist composition on a substrate, selectively exposing the resist film to radiation such as light or electron beam through a photomask having a predetermined pattern formed thereon, and subjecting the resist film to a development treatment to form a resist pattern having a predetermined shape on the resist film. A resist composition capable of being changing into characteristics wherein the exposed area is dissolved in a developing solution is referred to as a positive resist composition, while a resist composition capable of being changing into characteristics wherein the exposed area is not dissolved in a developing solution is referred to as a negative resist composition.
In the production of semiconductor devices and liquid crystal displays, rapid progress has recently been made in miniaturizing of a pattern with the progress of a lithography technology. As a technique for miniaturizing of the size, shortening of the wavelength of an exposure light source is generally performed. Specifically, while ultraviolet rays typified by g-ray and i-ray have hitherto been used, KrF excimer laser (248 nm) is now introduced and also ArF excimer laser (193 mm) having a shorter wavelength than that of the above excimer laser begins to be introduced. Also, a study about F2 excimer (157 nm) laser having a shorter wavelength than that of these excimer lasers, EUV (Extreme Ultraviolet ray), electron beam and X-ray have been made. Exposure to electron beam or EUV is usually conducted by exposure through a desired mask pattern or direct drawing in vacuum.
To reproduce a pattern having a fine size, a resist material having high resolution is required. As the resist material, a chemically amplified resist composition containing a base resin and an acid generator which generates an acid upon exposure is used. For example, a positive chemically amplified photoresist contains a resin component in which alkali solubility enhances by an action of an acid, and an acid generator component which generates an acid upon exposure. When an acid is generated from an acid generator upon exposure in the case of forming a resist pattern, the exposed area becomes soluble in an alkali.
As the resin component of the positive resist composition, for example, a resin in which a portion of hydroxyl groups of a polyhydroxystyrene-based resin are protected with an acid dissociable dissolution inhibiting group, or a resin in which a portion of carboxy groups of an acrylic resin are protected with an acid dissociable dissolution inhibiting group is used. As the acid dissociable dissolution inhibiting group, a so-called acetal group, for example, a chain ether group such as 1-ethoxyethyl group or a cyclic ether group such as tetrahydropyranyl group, tertiary alkyl group such as tert-butyl group, and a tertiary alkoxycarbonyl group such as tert-butoxycarbonyl group are mainly used (see, for example, Japanese Unexamined Patent Application, First Publication No. 2002-341538).
On the other hand, the photomask used in the case of forming a pattern comprises a transparent substrate and a shielding layer formed thereon in the form of a predetermined pattern. Also in the case of producing such a photomask, a resist composition is used similar to the above case. That is, a shielding substrate material comprising a transparent substrate (glass substrate) and a shielding layer (chromium oxide layer) made mainly of chromium oxide formed on the transparent substrate is prepared, and a resist film is formed on the chromium oxide layer. Then, the resist film is selectively exposed through a resist for forming a photomask and developed to form a resist pattern on the chromium oxide layer. Then, the chromium oxide layer of the area, on which no pattern is formed, is etched through the resist pattern as a mask and the pattern is transferred onto the chromium oxide layer to obtain a photomask comprising a glass substrate and a chromium oxide layer having a predetermined pattern formed thereon (see, for example, written by Isamu TANABE et al., “Lecture on Photomask Technology”, Kogyo Chosakai Publishing, Inc., First Edition, Aug. 20, 1996, pp. 10-19).
In the production of the photomask, the exposure is mainly conducted by direct drawing using electron beam because a fine pattern can be formed.